Some satellite systems include mobile satellite programs where multiple spot beams spread over a large geographic area that are engaged to connect a large number of mobile users to a gateway. Multiple spot beams can be generated using either a phased array or a reflector antenna with an array feed. Some systems may utilize many feed elements and may beamform combinations of these to generate multiple beams.
Beamforming is implemented by adjusting the amplitude and phase of each signal path routed to each feed element. Each individual signal path is routed to multiple feeds with relative amplitudes and phases which define each intended beam. On many satellite programs, beamforming is accomplished by constructing a fixed beamforming network behind the feed array. Satellite systems have employed an onboard digital signal processor (DSP) which performs digital beamforming allowing an entire beam pattern to be re-optimized at any time during the life of the spacecraft. The DSP, however, adds significant weight and power demands to the payload. Ground-based beamforming (GBBF) provides the same or greater flexibility than digital beamforming onboard the satellite without the weight and power penalty of an onboard DSP.
GBBF may require knowledge of the phase and/or amplitude variations caused by the return and forward links. Various satellite components, such as amplifiers, DSP, hybrid matrices, and diplexers, to name a few, may affect the phase and/or amplitude of a signal. There is a need in the art for ground-based systems and methods that determine the phase and/or amplitude effects of the forward and return link paths.